I think that it means that foreach (#blah alah blah) created an anonymous array, that can be reused :) I don't know if it is a bug or a feature of Perl :)

The anonymous array is not created only in the case of for(number..number), as ikegami mentioned, as such loops are replaced by counting ones.

The shortest illustrating example: 

for (0..2) {
  foreach my $x (0..1, ()) { print +($x .= " wassap? ") . "\n"; }
}

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It prints: 
0 wassap?
1 wassap?
0 wassap?  wassap?
1 wassap?  wassap?
0 wassap?  wassap?  wassap?
1 wassap?  wassap?  wassap?

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UPDATE:

B::Deparse displays that it ocuurs only to arrays generated by the .. operator.

UPDATE 2:

I just realised that i used the feature of modifyable '..' arrays in my code :) 

print map { s/$/\n/;$_ } (0..1);

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works, while 
print map { s/$/\n/;$_ } (0,1);

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produces a fatal error :) So we can create one more example: 
for (0..1) {
    print map { s/$/!\n/;$_ } (0..1);
}

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The bug is that anonymous arrays created by .. are globally scoped :) and I don't think it'a an optimisation for Perl.

Finally, i think that the title of the node is incorrect :)). The good title would be Unexpected behavior of '..' lists. Or smth like this :)

     s;;Just-me-not-h-Ni-m-P-Ni-lm-I-ar-O-Ni;;tr?IerONim-?HAcker ?d;print

In reply to Re: Unexpected behaviour with constant lists and foreach (and closures?) by Ieronim
in thread Unexpected behavior of '..' lists by Crackers2

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